Merge pull request sass#755 from sass/calcfunctions

* Update calculation functions documentation
* Add abs() Percentage breaking change page.

source/_data/documentation.yml

@@ -71,6 +71,7 @@ toc:
       - CSS Variable Syntax: /documentation/breaking-changes/css-vars/
       - Duplicate Variable Flags: /documentation/breaking-changes/duplicate-var-flags/
       - Default Exports: /documentation/breaking-changes/default-export/
+      - abs() Percentage: /documentation/breaking-changes/abs-percent/
   - Command Line: /documentation/cli/
     :children:
       - Dart Sass: /documentation/cli/dart-sass/

source/documentation/breaking-changes/abs-percent.md

@@ -0,0 +1,21 @@
+---
+title: 'Breaking Change: abs() Percentage'
+introduction: >
+  Sass has historically supported the `abs()` function. After CSS supported
+  calculations in Values and Units Level 4, we had to workaround
+  backwards-compatibility. However, for the `abs()` function we posses a
+  compatibility problem supporting the `%` unit.
+---
+
+The `abs()` global function in Sass supported the `%` unit as an input and would
+resolve the `abs()` function before resolving the `%` value. For instance, if
+the input was `abs(10%)` the function will return `10%`. As a result, if the
+value of `10%` represented `-50px` the function would return `-50px`.
+
+However, the CSS `abs()` abs function will resolve the `%` before resolving the
+function. Therefore if the value of `10%` represented `-50px`, `abs(10%)` would
+return `-10%` which in the browser would be `50px`.
+
+For this reason, we are deprecating the global abs() function with a percentage.
+To preserve the current behavior, use `math.abs()` instead.
+

source/documentation/breaking-changes/index.md

@@ -22,6 +22,10 @@ time-sensitive, so they may be released with new minor version numbers instead.
 
 These breaking changes are coming soon or have recently been released:
 
+* [Passing a percentage unit to the global `abs()` is
+  deprecated](/documentation/breaking-changes/abs-percent/) beginning in Dart
+  Sass 1.65.0.
+
 * [Passing `null` as an alpha channel to `new SassColor()` is changing
   behavior](/documentation/breaking-changes/null-alpha) beginning in Dart
   Sass 1.64.3.

source/documentation/values/calculations.md

@@ -156,59 +156,119 @@ CSS to unitless numbers:
   @debug calc(-infinity) < math.$min-number  // true
 {% endcodeExample %}
 
-## `min()` and `max()`
+## Calculation Functions
 
-{% compatibility 'dart: ">=1.11.0 <1.42.0"', 'libsass: false', 'ruby: false', 'feature: "Special function syntax"' %}
-  LibSass, Ruby Sass, and versions of Dart Sass prior to 1.11.0 *always* parse
-  `min()` and `max()` as Sass functions. To create a plain CSS `min()` or
-  `max()` call for those implementations, you can write something like
-  `unquote("min(#{$padding}, env(safe-area-inset-left))")` instead.
-
-  Versions of Dart Sass between 1.11.0 and 1.40.0, and between 1.40.1 and 1.42.0
-  parse `min()` and `max()` functions as [special functions] if they're valid
-  plain CSS, but parse them as Sass functions if they contain Sass features
-  other than interpolation, like variables or function calls.
-
-  Dart Sass 1.41.0 parses `min()` and `max()` functions as calculations, but
-  doesn't allow unitless numbers to be combined with numbers with units. This
-  was backwards-incompatible with the global `min()` and `max()` functions, so
-  that behavior was reverted.
-
-  [special functions]: /documentation/syntax/special-functions
+{% compatibility 'dart: "1.65.0"', 'libsass: false', 'ruby: false', 'feature: "Additional functions"' %}
+  Versions of Dart Sass subsequent to 1.65.0 handle the execution of these
+  calculation functions: `round()`, `mod()`, `rem()`, `sin()`, `cos()`, `tan()`,
+  `asin()`, `acos()`, `atan()`, `atan2()`, `pow()`, `sqrt()`, `hypot()`,
+  `log()`, `exp()`, `abs()`, and `sign()`.
 {% endcompatibility %}
 
-CSS added support for [`min()` and `max()` functions] in Values and Units Level
-4, from where they were quickly adopted by Safari [to support the iPhoneX]. But
-Sass supported its own [`min()`] and [`max()`] functions long before this, and
-it needed to be backwards-compatible with all those existing stylesheets. This
-led to the need for extra-special syntactic cleverness.
-
-[`min()` and `max()` functions]: https://drafts.csswg.org/css-values-4/#calc-notation
-[to support the iPhoneX]: https://webkit.org/blog/7929/designing-websites-for-iphone-x/
-[`min()`]: /documentation/modules/math#min
-[`max()`]: /documentation/modules/math#max
-
-If a `min()` or `max()` function call is a valid calculation expression, it will
-be parsed as a calculation. But as soon as any part of the call contains a
-SassScript feature that isn't supported in a calculation, like the [modulo
-operator], it's parsed as a call to Sass's core `min()` or `max()` function
-instead.
+Sass parses the following functions as [calculations]:
+* Comparison Functions: [`min()`], [`max()`], and [`clamp()`]
+* Stepped Value Functions: [`round()`], [`mod()`], and [`rem()`].
+* Trigonometric Functions: [`sin()`], [`cos()`], [`tan()`], [`asin()`], [`acos()`],
+  [`atan()`], and [`atan2()`].
+* Exponential Functions: [`pow()`], [`sqrt()`], [`hypot()`], [`log()`], and [`exp()`].
+* Sign-Related Functions: [`abs()`] and [`sign()`].
+
+[calculations]: https://www.w3.org/TR/css-values-4/#math
+[`min()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/min
+[`max()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/max
+[`clamp()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/clamp
+[`round()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/round
+[`abs()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/abs
+[`sin()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/sin
+[`cos()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/cos
+[`tan()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/tan
+[`asin()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/asin
+[`acos()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/acos
+[`atan()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/atan
+[`atan2()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/atan2
+[`pow()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/pow
+[`sqrt()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/sqrt
+[`hypot()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/hypot
+[`log()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/log
+[`exp()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/exp
+[`mod()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/mod
+[`rem()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/rem
+[`sign()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/sign
+
+### Legacy Global Functions
+
+CSS added support for [mathematical expressions] in Values and Units Level
+4. However, Sass supported its own [`round()`], [`abs()`], [`min()`] and
+[`max()`] long before this, and it needed to be backwards-compatible with all
+those existing stylesheets. This led to the need for extra-special syntactic
+cleverness.
+
+[mathematical expressions]: https://www.w3.org/TR/css-values-4/#math
+[`round()`]: ../modules/math#round
+[`abs()`]: ../modules/math#abs
+[`min()`]: ../modules/math#min
+[`max()`]: ../modules/math#max
+
+If a call to `round()`, `abs()`, `min()`, or `max()` is a valid calculation
+expression, it will be parsed as a calculation. But as soon as any part of the
+call contains a SassScript feature that isn't supported in a calculation, like
+the [modulo operator], it's parsed as a call to the appropriate Sass math
+function instead.
 
 Since calculations are simplified to numbers when possible anyway, the only
 substantive difference is that the Sass functions only support units that can be
 combined at build time, so `min(12px % 10, 10%)` will throw an error.
 
-[modulo operator]: /documentation/operators/numeric
+[modulo operator]: /documentation/operators/numeric/
 
 {% headsUp %}
   Other calculations don't allow unitless numbers to be added to, subtracted
-  from, or compared to numbers with units. `min()` and `max()` are different,
-  though: for backwards-compatibility with the global Sass `min()` and `max()`
-  functions which allow unit/unitless mixing for historical reasons, these units
-  can be mixed as long as they're contained directly within a `min()` or `max()`
+  from, or compared to numbers with units. [`min()`], [`max()`], [`abs()`] and
+  [single-argument `round()`] are different, though: for backwards-compatibility
+  with the global Sass legacy functions which allow unit/unitless mixing for
+  historical reasons, these units can be mixed as long as they're contained
+  directly within a `min()`, `max()`, `abs()`, or single-argument `round()`
   calculation.
+
+  For instance, `min(5 + 10px, 20px)` will result in `15px`. However
+  `sqrt(5 + 10px)` will throw an error, as `sqrt(5 + 10px)` was never a global
+  Sass function, and these are incompatible units.
+
+[single-argument `round()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/round
+[`abs()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/abs
+[`min()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/min
+[`max()`]: https://developer.mozilla.org/en-US/docs/Web/CSS/max
 {% endheadsUp %}
 
+#### `min()` and `max()`
+
+{% compatibility 'dart: ">=1.11.0 <1.42.0"', 'libsass: false', 'ruby: false', 'feature: "min and max syntax"' %}
+  LibSass, Ruby Sass, and versions of Dart Sass prior to 1.11.0 *always* parse
+  `min()` and `max()` as Sass functions. To create a plain CSS `min()` or
+  `max()` call for those implementations, you can write something like
+  `unquote("min(#{$padding}, env(safe-area-inset-left))")` instead.
+
+  CSS added support for [`min()` and `max()` functions] in Values and Units
+  Level 4, from where they were quickly adopted by Safari [to support the iPhoneX].
+  Since we already supported `min()` and `max()` as legacy Sass functions, we
+  had to implement logic for backwards-compatibility and for support as CSS
+  functions.
+
+  Versions of Dart Sass between 1.11.0 and 1.40.0, and between 1.40.1
+  and 1.42.0 parse `min()` and `max()` functions as [special functions] if
+  they're valid plain CSS, but parse them as Sass functions if they contain Sass
+  features other than interpolation, like variables or function calls.
+
+  Dart Sass 1.41.0 parses `min()` and `max()` functions as calculations, but
+  doesn't allow unitless numbers to be combined with numbers with units. This
+  was backwards-incompatible with the global `min()` and `max()` functions, so
+  that behavior was reverted.
+
+  [`min()` and `max()` functions]: https://www.w3.org/TR/css-values-4/#math
+  [to support the iPhoneX]: https://webkit.org/blog/7929/designing-websites-for-iphone-x/
+  [special functions]: /documentation/syntax/special-functions/
+{% endcompatibility %}
+
 {% codeExample 'min-max' %}
   $padding: 12px;
 
@@ -225,6 +285,7 @@ combined at build time, so `min(12px % 10, 10%)` will throw an error.
     padding-left: max($padding % 10, 20px);
     padding-right: max($padding % 10, 20px);
   }
+
   ===
   $padding: 12px
 
@@ -240,4 +301,108 @@ combined at build time, so `min(12px % 10, 10%)` will throw an error.
     // SassScript function calls.
     padding-left: max($padding % 10, 20px)
     padding-right: max($padding % 10, 20px)
+
+  ===
+  .post {
+    padding-left: max(12px, env(safe-area-inset-left));
+    padding-right: max(12px, env(safe-area-inset-right));
+  }
+
+  .sidebar {
+    padding-left: 20px;
+    padding-right: 20px;
+  }
 {% endcodeExample %}
+
+#### `round()`
+
+{% compatibility 'dart: "1.65.0"', 'libsass: false', 'ruby: false', 'feature: "min and max syntax"' %}
+  LibSass, Ruby Sass, and versions of Dart Sass prior to 1.65.0 *always* parse
+  `round()` as a Sass function. To create a plain CSS calculation for those
+  implementations, you can write something like
+  `round(#{$strategy, $number, $step})` instead.
+{% endcompatibility %}
+
+The [`round(<strategy>, number, step)`] function accepts an optional rounding
+strategy, a value to be rounded and a rounding interval `step`. `strategy`
+should be `nearest`, `up`, `down`, or `to-zero`.
+
+[`round(<strategy>, number, step)`]: https://developer.mozilla.org/en-US/docs/Web/CSS/round#parameter
+
+{% codeExample 'round' %}
+  $number: 12.5px;
+  $step: 15px;
+
+  .post-image {
+    // Since these round() calls are valid calculation expressions, they're
+    // parsed as calculations.
+    padding-left: round(nearest, $number, $step);
+    padding-right: round($number + 10px);
+    padding-bottom: round($number + 10px, $step + 10%);
+  }
+
+  ===
+  $number: 12.5px
+  $step: 15px
+
+  .post-image
+    // Since these round() calls are valid calculation expressions, they're
+    // parsed as calculations.
+    padding-left: round(nearest, $number, $step)
+    padding-right: round($number + 10px)
+    padding-bottom: round($number + 10px, $step + 10%)
+
+  ===
+  .post-image {
+    padding-left: 15px;
+    padding-right: 23px;
+    padding-bottom: round(22.5px, 15px + 10%);
+  }
+{% endcodeExample %}
+
+#### `abs()`
+
+{% compatibility 'dart: "1.65.0"', 'libsass: false', 'ruby: false', 'feature: "min and max syntax"' %}
+  LibSass, Ruby Sass, and versions of Dart Sass prior to 1.65.0 *always* parse
+  `abs()` as a Sass function. To create a plain CSS calculation for those
+  implementations, you can write something like `abs(#{$number})` instead.
+{% endcompatibility %}
+
+{% headsUp %}
+The global `abs()` function compatibiliy with [% unit parameters is deprecated].
+In the future, this will emit a CSS abs() function to be resolved by the browser.
+
+[% unit parameters is deprecated]: /documentation/breaking-changes/abs-percent/
+{% endheadsUp %}
+
+The [`abs(value)`] takes in a single expressiona as a parameter and returns the
+absolute value of `$value`. If `$value` is negative, this returns `-$value`, and if
+`$value` is positive, it returns `$value` as-is.
+
+[`abs(value)`]: https://developer.mozilla.org/en-US/docs/Web/CSS/abs
+
+{% codeExample 'abs' %}
+  .post-image {
+    // Since these abs() calls are valid calculation expressions, they're
+    // parsed as calculations.
+    padding-left: abs(10px);
+    padding-right: math.abs(-7.5%);
+    padding-top: abs(1 + 1px);
+  }
+
+  ===
+  .post-image
+    // Since these abs() calls are valid calculation expressions, they're
+    // parsed as calculations.
+    padding-left: abs(-10px)
+    padding-right: math.abs(-7.5%)
+    padding-top: abs(1 + 1px)
+
+  ===
+  .post-image {
+    padding-left: 10px;
+    padding-right: 7.5%;
+    padding-top: 2px;
+  }
+
+{% endcodeExample %}